Light control film

ABSTRACT

Disclosed is a light control film comprising: two transparent electroconductive resin substrates; and a light control layer sandwiched between the two transparent electroconductive resin substrates, the light control layer comprising: a resin matrix; and a light control suspension dispersed in the resin matrix, wherein at least one of the transparent electroconductive resin substrates has, on the light control layer side thereof, a primer layer, and the primer layer is made of a thin film comprising a material containing a (meth)acrylate having, in the molecule thereof, a hydroxyl group. Thus, it is possible to provide a light control film that improves the adhesion between a film matrix and a substrate, and that achieves a stable light control function.

TECHNICAL FIELD

The present invention relates to a light control film having a lightcontrol function.

BACKGROUND ART

Light control glass containing a light control suspension was firstinvented by Edwin Land. The form thereof has a structure wherein a lightcontrol suspension in a liquid state is injected between two transparentelectroconductive substrates having a narrow gap (see, for example,Patent Documents 1 and 2). According to Edwin Land's invention, in thestate that no electric field is applied to the liquid light controlsuspension, which is injected between the two transparentelectroconductive substrates, the great majority of light radiatedthereinto is reflected, scattered or absorbed on/in the light controlparticles dispersed in the suspension by Brownian movement of the lightcontrol particles. Only a very small portion thereof is transmittedtherethrough.

In other words, the degree of the transmission, reflection, scatteringor absorption is decided in accordance with the shape, nature andconcentration of the light control particles dispersed in the lightcontrol suspension, and the energy quantity of the radiated light. Whenan electric field is applied to a light control window wherein lightcontrol glass having the above-mentioned structure is used, the field ispassed through the transparent electroconductive substrates so that anelectric field is formed in the light control suspension. The lightcontrol particles, which show a light control function, are polarized sothat the particles are arranged in parallel to the electric field. As aresult, light is transmitted between the light control particles.Finally, the light control glass turns transparent. However, such aninitial light control device has not easily been put into practice usebecause of the aggregation of the light control particles in the lightcontrol suspension, the sedimentation based on the weight of theparticles themselves, a change in the color phase on the basis of heat,a change in the optical density, a deterioration based on the radiationof ultraviolet rays, difficulties in the maintenance of the intervalbetween the substrates and in the injection of the light controlsuspension into the interval, and others.

Rober L. Saxe, F. C. Lowell or R. I. Thompson discloses a light controlwindow using light control glass which compensates for problems ofinitial light control windows, that is, the aggregation and thesedimentation of light control particles, a change in the opticaldensity, and others (see, for example, Patent Documents 3 to 9).According to these patents and others, use is made of a liquid-statelight control suspension composed of light control crystal particles ina needle form, a suspending agent for dispersing the crystal particles,a dispersion adjustor, a stabilizer and others to make the density ofthe light control particles substantially equal to that of thesuspending agent, whereby the sedimentation of the light controlparticles is prevented while the addition of the dispersion adjustormakes the dispersibility of the light control particles high. In thisway, the aggregation of the light control particles is prevented so thatthe initial problems are solved. However, the light control glass has astructure wherein a light control suspension in a liquid state is sealedinto a gap between two transparent electroconductive substrates,similarly to any conventional light control glass; thus, when alarge-size product is produced, it is difficult to seal the suspensionevenly into the gap between the two transparent electroconductivesubstrates, so that there remains a problem that a difference inhydraulic pressure between the upper and lower regions of the producteasily causes an expansion phenomenon of the lower region. Additionally,in accordance with the external environment, for example, the pressureof wind, the interval between the substrates is changed, so that thefollowing problem is caused: the optical density is changed so that thecolor phase becomes uneven; or a sealing member in the surroundings, forstoring liquid between the transparent electroconductive substrates isbroken so that the light control material leaks. Moreover, the responsetime becomes uneven by a deterioration based on ultraviolet rays, or adrop in the voltage between the circumferential region of thetransparent electroconductive substrates and the center region thereof.

As a method for improving the above, suggested is a method of mixing aliquid light control suspension with a solution of a curable polymericresin, and using a phase-separation method using polymerization, aphase-separation method using solvent-volatilization, a phase-separationmethod depending on temperature, or some other method to produce a film(see, for example, Patent Document 10). However, about the polymericresin, which is to be cured to become a film matrix, the moleculethereof is not designed, considering the adhesiveness to a transparentelectroconductive substrate. Thus, poor is the adhesiveness between thefilm matrix and a substrate, such as a PET film having a surface onwhich a electroconductive thin film made of ITO or the like is formed,so that there remains a problem that these are very easily peeled fromeach other.

PRIOR ART LITERATURES Patent Literatures

-   Patent Literature 1: U.S. Pat. No. 1,955,923-   Patent Literature 2: U.S. Pat. No. 1,963,496-   Patent Literature 3: U.S. Pat. No. 3,756,700-   Patent Literature 4: U.S. Pat. No. 4,247,175-   Patent Literature 5: U.S. Pat. No. 4,273,422-   Patent Literature 6: U.S. Pat. No. 4,407,565-   Patent Literature 7: U.S. Pat. No. 4,422,963-   Patent Literature 8: U.S. Pat. No. 3,912,365-   Patent Literature 9: U.S. Pat. No. 4,078,856-   Patent Literature 10: JP-A No. 2002-189123

DISCLOSURE OF THE INVENTION Technical Problem

An object of the present invention is to provide a light control filmwherein the adhesiveness between a film matrix and a substrate isimproved to exhibit a stable light control function.

Solution to Problem

The inventors of the present invention have made eager investigations soas to find out that the above-mentioned problems can be solved by layinga specified primer layer on the light-control-layer-side surface of atleast one of the transparent electroconductive resin substrates.

Thus, the present invention relates to a light control film, comprising:two transparent electroconductive resin substrates; and a light controllayer sandwiched between the two transparent electroconductive resinsubstrates, the light control layer comprising: a resin matrix; and alight control suspension dispersed in the resin matrix, wherein at leastone of the transparent electroconductive resin substrates has, on thelight control layer side thereof, a primer layer, and the primer layeris made of a thin film comprising a material containing a (meth)acrylatehaving, in the molecule thereof, a hydroxyl group. It is preferred thatthis hydroxyl group is an alcoholic hydroxyl group.

More preferably, the (meth)acrylate, which has in the molecule thereof ahydroxyl group, is an acrylate having a pentaerythritol skeleton.

The primer layer may further contain oxide fine particles. It is alsopreferred that the (meth)acrylate having in the molecule thereof ahydroxyl group, is a thermally-cured or optically-cured acrylate.

In the present invention, the film thickness of the primer layer ispreferably 500 nm or less.

Effects of the Invention

The light control film of the present invention is high in theadhesiveness between the light control layer and the transparentelectroconductive resin substrates, so that the film can exhibit astable light control function.

The disclosure of the present application is related to the subjectmatters described in Japanese Patent Application No. 2008-210561 filedon Aug. 19, 2008, and the contents disclosed therein are incorporatedherein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a sectional structure of an aspect of alight control film of the present invention.

FIG. 2 are each a schematic view for describing the action of the lightcontrol film in FIG. 1 when no electric field is applied thereto.

FIG. 3 are each a schematic view for describing the action of the lightcontrol film in FIG. 1 when an electric field is applied thereto.

FIG. 4 is a schematic view for describing a state of an end region ofthe light control film. Illustration of light control particles 10 indroplets 3 is omitted.

BEST MODE FOR CARRYING OUT THE INVENTION

A light control film of the present invention is a light control filmwherein a light control layer comprising: a resin matrix; and a lightcontrol suspension dispersed in the resin matrix, is sandwiched betweentwo transparent electroconductive resin substrates, wherein a specifiedprimer layer is laid on a surface of at least one of the transparentelectroconductive resin substrates which is a surface contacting thelight control layer.

The light control layer can be generally formed by use of a lightcontrol material. The light control material contains the following: apolymeric medium that is irradiated with an energy ray to be cured, as aresin matrix; and a light control suspension wherein light controlparticles are dispersed in a dispersing medium in the state that theparticles can flow. It is preferred that the dispersing medium in thelight control suspension can undergo phase separation from the polymericmedium and from a cured product thereof. The light control film of thepresent invention is obtained by using the light control material andsandwiching the light control layer, wherein the light controlsuspension is dispersed in the resin matrix made of the polymericmedium, between the two transparent electroconductive resin substrateswhich each have a surface subjected to primer treatment and contactingthe light control layer, between the two transparent electroconductiveresin substrates only one of which has a surface subjected to primertreatment and contacting the light control layer, or between others. Inother words, in the light control layer of the light control film of thepresent invention, the light control suspension, which is a liquidstate, is dispersed in the form of fine droplets in the resin matrix,which is a solid state, obtained by curing the polymeric medium. Thelight control particles contained in the light control suspension arepreferably in the form of rods or needles.

When an electric field is applied to the light control film, the lightcontrol particles having an electric dipolar moment, which are floatedand dispersed in the droplets of the light control suspension dispersedin the resin matrix, are arranged in parallel to the electric field,whereby the droplets are converted to the state of being transparent toincident light, so that the film transmits the incident light in thestate that the light is hardly scattered in accordance with the viewingangle or the transparency is hardly declined. In the present invention,a light control layer is laid onto a specified primer layer to form afilm, thereby solving problems of any conventional light control film,that is, problems that the adhesiveness between its light control layerand its transparent electroconductive resin substrates is weak so thatthe light control layer is peeled from the transparent electroconductiveresin substrates in the production steps, a working step after theproduction of the film, or some other step.

In the present invention, about the (meth)acrylate having in themolecule thereof a hydroxyl group, as a material for forming the primerlayer, it is preferred that the hydroxyl group is an alcoholic hydroxylgroup. The (meth)acrylate having in the molecule thereof a hydroxylgroup, is more preferably an acrylate containing a pentaerythritolskeleton.

Hereinafter, the structure of each of the individual layers, and thelight control film will be described.

<Primer Layer>

First, a description will be made about the (meth)acrylate having in themolecule thereof a hydroxyl group and is used in the primer layer in thepresent invention. Examples of the (meth)acrylate having in the moleculethereof a hydroxyl group, include compounds represented by formula (1)to formula (8) illustrated below.

The (meth)acrylate having a hydroxyl group, is preferably a(meth)acrylate having a hydroxyl group and a pentaerythritol skeleton.In the “(meth)acrylate having a hydroxyl group and a pentaerythritolskeleton”, all the hydroxyl groups of the pentaerythritol may besubstituted as far as the hydroxyl group is present inside the(meth)acrylate molecule. The “(meth)acrylate” is preferably a(meth)acrylate wherein at least one of the hydroxyl groups ofpentaerythritol is unsubstituted.

As a material for forming the primer layer, any (meth)acrylate describedbelow may be used besides the (meth)acrylate having in the moleculethereof a hydroxyl group and the more preferably used (meth)acrylatehaving a hydroxyl group and a pentaerythritol skeleton. The usable(meth)acrylate is, for example, a compound as described in thefollowing, but is not limited thereto in the present invention: anacrylic acid ester such as sorbitol tetraacrylate,2-hydroxy-3-acryloyloxypropyl methacrylate, 2-hydroxy-3-phenoxypropylacrylate, 2-acryloyloxy-2-hydroxyethylphthalic acid, a methacrylic acidadduct of ethylene glycol diglycidyl ether, an acrylic acid adduct oftripropylene glycol diglycidyl ether, a methacrylic acid or acrylic acidadduct of bisphenol A diglycidyl ether, a methacrylic acid or acrylicacid adduct of diglycidyl ether to which 2 moles of bisphenol Apropylene oxide is added, 2-hydroxyethyl methacrylate, 2-hydroxypropylmethacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,2-hydroxybutyl methacrylate, or sorbitol pentaacrylate; a methacrylicacid ester such as pentaerythritol dimethacrylate, pentaerythritoltrimethacrylate, sorbitol tetramethacrylate, dipentaerythritoldimethacrylate, dipentaerythritol trimethacrylate, or dipentaerythritoltetramethacrylate; a crotonic acid ester such as pentaerythritoldicrotonate, or pentaerythritol tricrotonate; or an itaconic acid ester,such as pentaerythritol diitaconate, pentaerythritol triitaconate,dipentaerythritol triitaconate, or dipentaerythritol pentaitaconate.

As a material for forming the primer layer, the following may be furthercontained: a urethane acrylate containing a pentaerythritol skeleton, ora urethane acrylate containing both of a pentaerythritol skeleton and anIPDI (3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate) skeleton.Specific examples thereof include compounds represented by the followingformula (9) to formula (15):

In each of the formula (13) to formula (15), R's may be the same ordifferent, and are each a group illustrated below. At least one of R'sis preferably H.

In the “urethane acrylate containing a pentaerythritol skeleton” as thematerial used together to form the primer layer, the “pentaerythritolskeleton” has a structure represented by the following formula (a):

Specifically, the “urethane acrylate containing a pentaerythritolskeleton” has a structure wherein at least one hydrogen in the hydroxylgroups of pentaerythritol present in the molecule of the urethaneacrylate is substituted with a carbamoyl group and further at least oneof the hydroxyl groups is esterified with (meth)acrylic acid. At thistime, the carbamoyl group and/or (meth)acrylic acid may (each) have asubstituent. The hydroxyl group substituted with the carbamoyl group andthe hydroxyl group esterified with (meth)acrylic acid do not need to behydroxyl groups bonded to the same pentaerythritol skeleton representedby the formula (a).

It is also preferred that the urethane acrylate containing apentaerythritol skeleton in the present invention has, as thepentaerythritol skeleton thereof, dipentaerythritol wherein two arelinked to each other through oxygen. In this case also, at least onehydrogen of the hydroxyl groups of the pentaerythritol is substitutedwith a carbamoyl group and further at least one of the hydroxyl groupsis esterified with (meth)acrylic acid. At this time, the carbamoyl groupand/or (meth)acrylic acid may (each) have a substituent.

The “IPDI (3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate)skeleton” denotes a structure represented by the following formula (b):

It is preferred that the primer layer further contains oxide fineparticles.

Examples of the oxide that may be contained in the primer layer includeSiO₂, ITO, ZrO₂, TiO₂, Bi₂O₃, Al₂O₃, Y₂O₃, CeO₂, ZnO, CuO, Sn₂O, andcobalt blue. The oxide is more preferably any one of SiO₂, ITO and ZrO₂,or a mixture thereof.

When the oxide fine particles are added, as a filler, to the primerlayer, the primer layer can gain a high hardness so as to produce aneffect that when the light control film is peeled to take outelectrodes, an underlying transparent electroconductive film is noteasily injured or scratched.

The addition of the oxide fine particles to the primer layer may make itpossible to adjust the surface energy of the primer layer to produce anadhesiveness-improving effect.

The particle diameter of the oxide fine particles is preferably 50 nm orless from the viewpoint of a restraint of a rise in the haze of thelight control film.

The average particle diameter in the present invention is the particlediameter calculated out by use of the following equation based on thespecific surface area obtained by making a measurement with a surfacearea measuring device according to the BET method:

Average particle diameter (nm)=6000/(Density [g/cm³]×Specific surfacearea [m²/g])

It is advisable that about the metal oxide fine particles having anaverage particle diameter in the above-mentioned range, an appropriateproduct is selected from commercially available products.

The content by percentage of the oxide fine particles in the primerlayer is preferably 30% or less by mass of the whole of the materials ofthe primer layer from the viewpoint of a restraint of a rise in the hazeof the light control film.

The (meth)acrylate having in the molecule thereof a hydroxyl group usedin the present invention, can be synthesized by a known synthesisprocess. In a case where the ester is, for example, an epoxy ester, theester can be obtained by causing an epoxy compound and (meth)acrylicacid to react with each other in an inert gas in the presence of anesterifying catalyst and a polymerization inhibitor.

Examples of the inert gas include nitrogen, helium, argon, and carbondioxide. These may be used alone or in combination.

The esterifying catalyst may be, for example, a compound having tertiarynitrogen, such as triethylamine, a pyridine derivative or an imidazolederivative, a phosphorus compound such as trimethylphosphine ortriphenylphosphine, or an amine salt such as tetramethylammoniumchloride or triethylamine. The addition amount thereof is from 0.000001to 20% by mass, preferably from 0.001 to 1% by mass.

The polymerization inhibitor may be a polymerization inhibitor that isitself known, such as hydroquinone or tert-butylhydroquinone. The useamount thereof is selected from the range of 0.000001 to 0.1% by mass.

Examples of the epoxy ester include 2-hydroxy-3-phenoxypropyl acrylate(trade name: ARONIX M-5700, manufactured by Toagosei Co., Ltd., or tradename: EPOXY ESTER M-600A, manufactured by Kyoeisha Chemical Co., Ltd.),2-hydroxy-3-acryloyloxypropyl methacrylate (trade name: LIGHT ESTERG-201P, manufactured by Kyoeisha Chemical Co., Ltd.), and a glycerindiglycidyl ether acrylic-acid-adduct (trade name: EPOXY ESTER 80MFA,manufactured by Kyoeisha Chemical Co., Ltd.).

In the case of the (meth)acrylate having a hydroxyl group and apentaerythritol skeleton, this ester can be obtained by causingpentaerythritol, dipentaerythritol or the like to react with acrylicacid or methacrylic acid in the air in the presence of an esterifyingcatalyst and a polymerization inhibitor. The method for reaction foradding acrylic acid or methacrylic acid to pentaerythritol ordipentaerythritol may be a known method described in JP-B No. 5-86972,JP-A No. 63-68642, and others.

Specific examples of a commercially available product containing the(meth)acrylate having a hydroxyl group and a pentaerythritol skeletoninclude AY42-151 (a mixture of a dipentaerythritol type acrylate, amethacrylic acid monomer and a siloxane compound, containing SiO₂ fineparticles as a filler, and manufactured by Dow Corning Toray Co., Ltd.),and ARONIX M-305 (a mixture of pentaerythritol acrylate andpentaerythritol tetraacrylate, containing no filler and manufactured byToagosei Co., Ltd.), and UVHC 7000 (an IPDI-skeleton-containingpentaerythritol type urethane acrylate, containing no filler andmanufactured by Momentive Performance Materials Japan LLC).

The urethane acrylate containing pentaerythritol skeleton can besynthesized by a known method. For example, urethane acrylate isgenerally obtained by causing hydroxyl groups of a polyol compound, apolyisocyanate compound or the like to react with ahydroxyl-group-containing (meth)acrylate to react with each other by aknown method; therefore, in the same way, the urethane acrylatecontaining pentaerythritol skeleton can be produced by, for example, anyone of the following production methods 1 to 4:

(Production method 1): a method of charging a polyol compound, apolyisocyanate compound, and a pentaerythritol-skeleton-containing(meth)acrylate at a time so as to be caused to react with each other;

(Production method 2): a method of causing a polyol compound and apolyisocyanate compound to react with each other, and next causing theresultant to react with a pentaerythritol-skeleton-containing(meth)acrylate;

(Production method 3): a method of causing a polyisocyanate compound anda pentaerythritol-skeleton-containing (meth)acrylate to react with eachother, and next causing the resultant to react with a polyol compound;and

(Production method 4): a method of causing a polyisocyanate compound anda pentaerythritol-skeleton-containing (meth)acrylate to react with eachother, next causing the resultant to react with a polyol compound, andfinally causing the resultant to react also with thepentaerythritol-skeleton-containing (meth)acrylate.

In these reactions, a catalyst may be used. For example, a tin basedcatalyst such as dibutyltin laurate, or a tertiary amine catalyst isused.

Examples of the pentaerythritol-skeleton-containing (meth)acrylate usedin the production methods 1 to 4 include pentaerythritol diacrylate,pentaerythritol triacrylate, dipentaerythritol pentaacrylate,dipentaerythritol tetraacrylate, and other hydroxyl-group-containing(meth)acrylates.

Examples of the polyisocyanate compound used in the production methods 1to 4 include 2,4-tolylenediisocyanate, 2,6-tolylenediisocyanate,1,3-xylylenediisocyanate, 1,4-xylylenediisocyanate,1,5-naphthalenediisocyanate, m-phenylenediisocyanate,p-phenylenediisocyanate, 3,3′-dimethyl-4,4′-diphenylmethanediisocyanate,4,4′-diphenylmethanediisocyanate, 3,3′-diphenylmethanediisocyanate,4,4′-biphenylenediisocyanate, 1,6-hexanediisocyanate,isophoronediisocyanate(3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate),methylenebis(4-cyclohexylisocyanate),2,2,4-trimethylhexamethylenediisocyanate, 1,4-hexamethylenediisocyanate,bis(2-isocyanatoethyl) fumarate, 6-isopropyl-1,3-phenyldiisocyanate,4-diphenylpropanediisocyanate, and lysinediisocyanate.

The urethane acrylate containing a pentaerythritol skeleton may be acommercially available product containing a urethane acrylate containingpentaerythritol Skelton. Examples thereof include UA-306H, UA-306I,UA-306T, and UA-510 (each manufactured by Kyoeisha Chemical Co., Ltd.).

The urethane acrylate containing both of a pentaerythritol skeleton andan IPDI skeleton can be obtained by use of isophoronediisocyanate as thepolyisocyanate compound in any one of the production methods 1 to 4.

It is preferred that a thermopolymerization initiator or aphotopolymerization initiator is used to cure the (meth)acrylate havingin the molecule thereof a hydroxyl group, used for the formation of theprimer layer, optionally together with the following compound, therebyforming a thin film: a (meth)acrylate other than it, a urethane acrylatecontaining a pentaerythritol skeleton, or a urethane acrylate containingboth of an IPDI (3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate)skeleton, and a pentaerythritol skeleton. The method for the thermalcuring and the method for the photocuring are not particularly limited,and may each be an ordinary curing method.

The thermopolymerization initiator used in the present invention may beany agent that is decomposed by heat, so as to generate radicals,thereby making it possible to start the polymerization of apolymerizable compound. Radical initiators useful therefor are knowninitiators, examples thereof include organic peroxides, and azonitriles.However, the initiator is not limited thereto. Examples of the organicperoxides include alkyl peroxides, aryl peroxides, acyl peroxides, aroylperoxides, ketone peroxides, azonitriles, peroxycarbonate, andperoxycarboxylate.

Examples of the alkyl peroxides include diisopropyl peroxide,di-tert-butyl peroxide, di-tert-amyl peroxide, tert-butylperoxy-2-ethylhexanoate, tert-amylperoxy-2-ethyl hexanoate, and tert-butylhydroperoxide.

Examples of the aryl peroxide include dicumyl peroxide, and cumylperoxide. Examples of the acyl peroxides include dilauroyl peroxide.

Examples of the aroyl peroxides include dibenzoyl peroxide.

Examples of the ketone peroxides include methyl ethyl ketone peroxide,and cyclohexanone peroxide.

Examples of the azonitriles include azobisisobutyronitrile, andazobisisopropylnitrile.

Examples of commercially available products of the thermopolymerizationinitiator include PEROYL IB, PERCUMYL ND, PEROYL NPP, PEROYL IPP, PEROYLSBP, PEROCTA ND, PEROYL TCP, PERROPYL OPP, PERHEXYL ND, PERBUTYL ND,PERBUTYL NHP, PERHEXYL PV, PERBUYTL PV, PEROYL 355, PEROYL L, PEROCTA O,PEROYL SA, PERHEXA 250, PERHEXYL O, NYPER PMB, PERBUTYL O, NYPER BMT,NYPER BW, PERHEXA MC and PERHEXA TMH (each manufactured by NOF Corp.);and azo compounds, in particular,2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(2-methyl-butyronitrile),2,2′-azobis(N-(2-propenyl)-2-methylpropionamide) and/or dimethyl2,2′-azobis(2-methylpropionate), and dimethyl 2,2′-azoisobutyrate.

The photopolymerization initiator may be any agent that is dissolved byirradiation with light, so as to generate radicals, thereby making itpossible to start the polymerization of a polymerizable compound.Examples thereof include acetophenone, acetophenone benzyl ketal,1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-2-phenylacetophenone,xanthone, fluorenone, benzaldehyde, anthraquinone, triphenylamine,carbazole, 3-methylacetophenone, 4-chlorobenzophenone,4,4′-dimethoxybenzophenone, 4,4′-diaminobenzophenone, Michler's ketones,benzoin propyl ether, benzoin ethyl ether, benzyl dimethyl ketal,1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one,2-hydroxy-2-methyl-1-phenylpropane-1-one, thioxanthone,diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone,2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propane-1-one,2,4,6-trimethylbenzoyldiphenylphosphine oxide, andbis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.However, the initiator is not limited thereto.

Examples of commercially available products of the photopolymerizationinitiator include IRGACURE 651, IRGACURE 184, IRGACURE 500, IRGACURE2959, IRGACURE 127, IRGACURE 754, IRGACURE 907, IRGACURE 369, IRGACURE379, IRGACURE 379EG, IRGACURE 1300, IRGACURE 819, IRGACURE 819DW,IRGACURE 1800, IRGACURE 1870, IRGACURE 784, IRGACURE OXE01, IRGACUREOXE02, IRGACURE 250, IRGACURE PAG103, IRGACURE PAG108, IRGACURE PAG121,IRGACURE PAG203, DAROCURE 1173, DAROCURE MBF, DAROCURE TPO, DAROCURE4265, DAROCURE EDB, and DAROCURE EHA (each manufactured by Ciba JapanK.K.); C0014, B1225, D1640, D2375, D2963, M1245, B0103, C1105, C0292,E0063, P0211, I0678, P1410, P1377, M1209, F0362, B0139, B1275, B0481,D1621, B1267, B1164, C0136, C1485, I0591, F0021, A0061, B0050, B0221,B0079, B0222, B1019, B1015, B0942, B0869, B0083, B2380, B2381, D1801,D3358, D2248, D2238, D2253, B1231, M0792, A1028, B0486, T0157, T2041,T2042, T1188 and T1608 (each manufactured by Tokyo Chemical IndustryCo., Ltd.).

In the present invention, the film thickness of the primer layer ispreferably 500 nm or less, more preferably from 1 to 500 nm. Thethickness is preferably from 10 to 500 nm, more preferably from 10 to500 nm, even more preferably from 10 to 100 nm. If the film thickness isless than 1 nm, the film tends to be unable to express a sufficientbonding force. If the film thickness is more than 500 nm, the tackinessof the primer layer becomes strong so that the following inconveniencetends to be easily caused: after the primer layer is applied onto atransparent electroconductive resin substrate film and the resultant iswound around a roll, the primer layer is transferred onto the rearsurface of the transparent electroconductive resin substrate film; orwhen a light control film is produced, the positioning of the substratefilm to be laminated onto the primer layer becomes difficult.

The film thickness of the primer layer can be measured by reflectometryof ultraviolet rays or visible rays, X-ray reflectivity analysis,ellipsometry or the like.

<Light Control Layer>

The light control layer in the present invention includes a lightcontrol material containing a resin matrix and a light controlsuspension dispersed in the resin matrix. The resin matrix includes apolymeric medium, and the light control suspension is a material whereinlight control particles are dispersed in a dispersing medium in thestate that the particles can flow. As the polymeric medium and thedispersing medium (dispersing medium in the light control suspension),use is made of a polymeric medium and a dispersing medium that make thefollowing possible: when the polymeric medium and a cured producttherefrom can undergo phase-separation from the dispersing medium atleast when these materials have been formed into a film. It is preferredto use a combination of a polymeric medium and a dispersing medium thatare incompatible with each other or are partially compatible with eachother.

The polymeric medium used in the present invention may be a compositionwhich contains (A) a resin with a substituent having an ethylenicallyunsaturated bond, and (B) a photopolymerization initiator, and thepolymeric medium is irradiated with an energy beam such as ultravioletrays, visible rays, an electron beam, thereby being cured. The resin(A), which has an ethylenically unsaturated bond, is preferably asilicone resin, an acrylic resin, a polyester resin or some other fromthe viewpoint of easiness in the synthesis thereof, the light controlperformances and endurance thereof, and others. It is preferred from theviewpoint of the light control performances and the endurance that thepreferred resin has, as a substituent thereof, an alkyl group such as amethyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, amyl,isoamyl, hexyl or cyclohexyl group, or an aryl group such as a phenyl ornaphthyl group.

Specific examples of the silicone resin include resins described in JP-BNo. 53-36515, JP-B No. 57-52371, JP-B No. 58-53656, and JP-B No.61-17863.

The silicone resin is synthesized by causing the following to undergodehydrogenation condensation reaction and dealcoholization reaction inthe presence of an organic tin catalyst such as 2-ethylhexanetin: asilanol-both-terminated siloxane polymer, such assilanol-both-terminated polydimethylsiloxane, silanol-both-terminatedpolydiphenylsiloxane-dimethylsiloxane copolymer orsilanol-both-terminated polydimethyldiphenylsiloxane; atrialkylalkoxysilane such as trimethylethoxysilane; a silane compoundcontaining an ethylenically unsaturated bond, such as(3-acryloxypropyl)methyldimethoxysilane; and some other compound. Theform of the silicone resin is preferably of a solvent-free type. Inother words, in the case of using a solvent for the synthesis of thesilicone resin, it is preferred to remove the solvent after thesynthesis reaction.

About the charging formulation of the individual raw materials when thesilicone resin is produced, the amount of the silane compound containingthe ethylenically unsaturated bond, such as(3-acryloxypropyl)methoxysilane is preferably from 19 to 50% by mass ofthe total of the siloxane(s) and the silane compound(s) as the startingmaterials, more preferably from 25 to 40% by mass thereof. If the amountof the silane compound containing the ethylenically unsaturated bond isless than 19% by mass, the ethylenically unsaturated bond concentrationin the finally-obtained resin tends to be far lower than a desiredconcentration. If the concentration is more than 50% by mass, theethylenically unsaturated bond concentration in the resultant resintends to be far higher than a desired concentration.

The acrylic resin can be obtained, for example, by copolymerizing amonomer for forming main-chain, such as an alkyl(meth)acrylate, anaryl(meth)acrylate, benzyl(meth)acrylate or styrene, with a monomerwhich contains a functional group for the introduction of anethylenically unsaturated bond, such as (meth)acrylic acid,hydroxyethyl(meth)acrylate, isocyanatoethyl(meth)acrylate orglycidyl(meth)acrylate, to synthesize a prepolymer once; and nextcausing the prepolymer to undergo addition reaction with a monomer suchas glycidyl(meth)acrylate, isocyanatoethyl(meth)acrylate,hydroxyethyl(meth)acrylate, (meth)acrylic or some other monomer in orderto cause the monomer to react with the functional group of theprepolymer.

The polyester resin is not particularly limited, and may be a resin thatcan easily be produced by a known method.

The average molecular weight of (A) the resin having the ethylenicallyunsaturated bond is preferably in the range of 20,000 to 100,000, morepreferably in the range of 30,000 to 80,000, the molecular weight beinga weight-average molecular weight in terms of polystyrene and beingobtained by gel permeation chromatography.

The ethylenically unsaturated bond concentration in the resin having theethylenically unsaturated bond is preferably in the range of 0.3 to 0.5mol/kg. If this concentration is less than 0.3 mol/kg, end regions ofthe light control film are not easily processed so that the transparentelectrodes opposite to each other easily short-circuit therebetween.Thus, the light control film tends to give a poor electricalreliability. By contrast, if the concentration is more than 0.5 mol/kg,the cured polymeric medium is easily dissolved into the dispersingmedium, which constitutes the droplets of the light control suspension,so as to give a tendency that the dissolved polymeric medium hinders themovement of the light control particles in the droplets so that thelight control performance tends to decline.

The ethylenically unsaturated bond concentration in (A) the resin havingthe ethylenically unsaturated bond is obtained from the ratio betweenintegrated-intensities of hydrogen according to NMR. When the conversionrate of the charged raw material into the resin is known, theconcentration is also obtained by calculation.

(B) The photopolymerization initiator used in the polymeric medium maybe a compound described in J. Photochem. Sci. Technol., 2, 283 (1977),specific examples thereof including2,2-dimethoxy-1,2-diphenylethane-1-one,1-(4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methyl-1-propane-1-one,bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide,2-hydroxy-2-methyl-1-phenylpropane-1-one, and(1-hydroxycyclohexyl)phenyl ketone.

The use amount of (B) the photopolymerization initiator is preferably inthe range of 0.1 to 20 parts by mass, more preferably in the range of0.2 to 10 parts by mass relative to 100 parts by mass of (A) the resin.

Besides (A) the resin having the substituent having the ethylenicallyunsaturated bond, the following may be used as a constituting materialof the polymeric medium: an organic solvent soluble resin or athermoplastic resin, such as polyacrylic acid or polymethacrylic acidhaving a weight-average molecular weight in the range of 1,000 to100,000, the molecular weight being a molecular weight in terms ofpolystyrene and being measured by gel permeation chromatography.

An additive, such as a coloration inhibitor such as dibutyltindilaurate, may be added into the polymeric medium if necessary. Thepolymeric medium may contain a solvent. The solvent may betetrahydrofuran, toluene, heptane, cyclohexane, ethyl acetate, ethanol,methanol, isoamyl acetate, hexyl acetate or the like.

It is preferred to use, as the dispersing medium of the light controlsuspension, a liquid copolymer which: fulfils a function of a dispersingmedium in the light control suspension; adheres onto the light controlparticles selectively to cover the particles so that at the time ofphase separation thereof from the polymeric medium, the dispersingmedium acts to cause the particles to be shifted to the phase-separateddroplet phase; and has neither electroconductivity nor affinity with thepolymeric medium.

The liquid copolymer is preferably, for example, a (meth)acrylic acidester oligomer having fluoro groups and/or hydroxyl groups, morepreferably a (meth)acrylic acid ester oligomer having fluoro groups andhydroxyl groups. When such a liquid copolymer is used, the monomer unitsof either the fluoro groups or the hydroxyl groups are faced toward thelight control particles. The monomer units of the other function tocause the light control suspension to be stably kept as droplets in thepolymeric medium. Therefore, the light control particles are veryhomogeneously dispersed in the light control suspension, and at the timeof the phase separation the light control particles are introduced intothe phase-separated droplets.

The (meth)acrylic acid ester oligomer having fluoro groups and/orhydroxyl groups may be an oligomer obtained by using afluoro-group-containing monomer and/or a hydroxyl-group-containingmonomer, and carrying out copolymerization with the monomer(s). Specificexamples thereof include 2,2,2-trifluoroethyl methacrylate/butylacrylate/2-hydroxyethyl acrylate copolymer, 3,5,5-trimethylhexylacrylate/2-hydroxypropyl acrylate/fumaric acid copolymer, butylacrylate/2-hydroxyethyl acrylate copolymer, 2,2,3,3-tetrafluoropropylacrylate/butyl acrylate/2-hydroxyethyl acrylate copolymer,1H,1H,5H-octafluoropentyl acrylate/butyl acrylate/2-hydroxyethylacrylate copolymer, 1H,1H,2H,2H-heptadecafluorodecyl acrylate/butylacrylate/2-hydroxyethyl acrylate copolymer, 2,2,2-trifluoroethylmethacrylate/butyl acrylate/2-hydroxyethyl acrylate copolymer,2,2,3,3-tetrafluoropropyl methacrylate/butyl acrylate/2-hydroxyethylacrylate copolymer, 1H,1H,5H-octafluoropentyl methacrylate/butylacrylate/2-hydroxyethyl acrylate copolymer,1H,1H,2H,2H-heptadecafluorodecyl methacrylate/butylacrylate/2-hydroxyethyl acrylate copolymer. The (meth)acrylic acid esteroligomers each preferably have both of fluoro groups and hydroxylgroups.

The weight-average molecular weight of these (meth)acrylic acid esteroligomers is preferably in the range of 1,000 to 20,000, more preferablyin the range of 2,000 to 10,000, the molecular weight being a molecularweight in terms of standard polystyrene and being measured by gelpermeation chromatography.

The use amount of the fluoro-group-containing monomer that is one of thestarting materials of each of these (meth)acrylic acid ester oligomersis preferably in the range of 6 to 12% by mole of the total of monomersthat are the starting materials, more effectively in the range of 7 to8% by mole thereof. If the use amount of the fluoro-group-containingmonomer is more than 12% by mole, the refractive index tends to becomelarge so that the light transmittance falls. The use amount of thehydroxyl-group-containing monomer that is one of the starting materialsof each of these (meth)acrylic acid ester oligomers is preferably in therange of 0.5 to 22.0 by mole, more preferably in the range of 1 to 8% bymole. If the use amount of the hydroxyl-group-containing monomer is morethan 22.0 by mole, the refractive index tends to become large so thatthe light transmittance falls.

The light control suspension used in the present invention is asubstance wherein light control particles are dispersed in thedispersing medium in the state that the particles can flow. As the lightcontrol particles, for example, the following are preferably used:needle-form small crystals of a polyiodide produced by causing iodineand a iodide to react with one material selected from the groupconsisting of pyrazine-2,3-dicarboxylic acid dihydrate,pyrazine-2,5-dicarboxylic acid dihydrate, and pyridine-2,5-dicarboxylicacid monohydrate, which are each a precursor of the light controlparticles, in the presence of a polymeric dispersing agent that is notaffinitive with the polymeric medium or the resin component in thepolymeric medium, that is, (A) the resin with the substituent having theethylenically unsaturated bond, and that is further capable of makingthe dispersibility of the light control particles high. A usable exampleof the polymeric dispersing agent is nitrocellulose. The iodide may becalcium iodide or the like. Examples of the thus-obtained polyiodideinclude compounds represented by the following general formulae:

CaI₂(C₆H₄N₂O₄).XH₂O wherein X: 1 to 2, and

CaI_(a)(C₆H₄N₂O₄)_(b) .cH₂O wherein a: 3 to 7, b: 1 to 2, and c: 1 to 3.

These polyiodides are each preferably a needle crystal.

For the light control particles for the light control film, for example,light control particles disclosed in the following may be used: U.S.Pat. No. 2,041,138 (E. H. Land); U.S. Pat. No. 2,306,108 (Land et al.);U.S. Pat. No. 2,375,963 (Thomas); U.S. Pat. No. 4,270,841 (R. L. Saxe);and GB Patent No 433,455. The polyiodide crystals known by these patentsare each produced by selecting one from pyrazine carboxylic acids andpyridine carboxylic acids, and causing the selected acid to react withiodide, chlorine or bromine so as to be turned to a polyhalide such aspolyiodide, polychloride or polybromide. The polyhalide is a complexcompound obtained by causing a halogen atom to reacts with an inorganicor organic material. Details of the production process thereof aredisclosed in, for example, U.S. Pat. No. 4,422,963 issued to Saxe.

In the step of synthesizing the light control particles, in order tomake the light control particles into an even size and improve thedispersibility of the light control particles in the specifieddispersing medium, it is preferred to use, as the polymeric dispersingagent, a polymeric material such as nitrocellulose, as disclosed bySaxe. However, when nitrocellulose is used, crystals covered withnitrocellulose are obtained. In the case of using such crystals as thelight control particles, the light control particles may not float inthe droplets separated at the time of the phase separation, so as toremain the resin matrix. In order to prevent this, it is preferred touse a silicone resin with a substituent having an ethylenicallyunsaturated bond as (A) the resin with the substituent having theethylenically unsaturated bond in the polymeric medium. The use of thesilicone resin makes it possible that the light control particles areeasily dispersed and floated in fine droplets formed by the phaseseparation in the production of the film. As a result, a better variableability can be obtained.

Besides the light control particles, use is made of, for example, aninorganic fiber such as carbon fiber, or a phthalocyanine compound suchas τ type metal-free phthalocyanine or a metal phthalocyanine. Examplesof the central metal in the phthalocyanine compound include copper,nickel, iron, cobalt, chromium, titanium, beryllium, molybdenum,tungsten, aluminum, and chromium.

In the present invention, the size of the light control particles ispreferably 1 μm or less, more preferably in the range of 0.1 to 1 μm,even more preferably in the range of 0.1 to 0.5 μm. If the size of thelight control particles is more than 1 μm, light is scattered thereon,the orientation movement of the particles is declined in the lightcontrol suspension when an electric field is applied thereto, and someother is caused, so that there is caused a problem that the transparencymay be declined. The size of the light control particles is defined asthe volume-average particle diameter measured with a submicron particleanalyzer (N4MD, manufactured by Beckman Coulter, Inc.) according tophoton correlation spectrometry.

The light control suspension used in the present invention is preferablycomposed of 1 to 70% by mass of the light control particles and 30 to99% by mass of the dispersing medium, and is more preferably composed of4 to 50% by mass of the light control particles and 50 to 96% by mass ofthe dispersing medium. In the present invention, the refractive index ofthe polymeric medium is preferably close to that of the dispersingmedium. Specifically, the difference in refractive index between thepolymeric medium and the dispersing medium in the present invention ispreferably 0.005 or less, more preferably 0.003 or less. The lightcontrol material contains the light control suspension in an amountusually in the range of 1 to 100 parts by mass, preferably in the rangeof 6 to 70 parts by mass, more preferably in the range of 6 to 60 partsby mass relative to 100 parts by mass of the polymeric medium.

<Transparent Electroconductive Resin Substrates>

In general, the transparent electroconductive resin substrates used whenthe light control material according to the present invention is used toproduce a light control film may each be a transparent electroconductiveresin substrate having a light transmittance of 80% or more and having asurface resistance value of 3 to 3000Ω wherein a transparent resinsubstrate is coated with a transparent electroconductive film (an ITO,SnO₂, In₂O₃ or organic conductive film, or some other film). The lighttransmittance may be measured according to the method for measuringtotal light ray transmittance in JIS K7105. The transparent resinsubstrate may be, for example, a polymeric film.

The polymeric film is, for example, a film of a polyester such aspolyethylene terephthalate, a film of a polyolefin such aspolypropylene, polyvinyl chloride film, an acrylic resin film, apolyethersulfone film, a polyarylate film, a polycarbonate film, or someother resin film. A polyethylene terephthalate film is preferred sincethe film is excellent in transparency, formability, bondability,workability, and others.

The thickness of the transparent electroconductive film with which thetransparent resin substrate is coated is preferably in the range of 10to 5,000 nm. The thickness of the transparent resin substrate is notparticularly limited. When the substrate is, for example, a polymericfilm, the thickness is preferably in the range of 10 to 200 μm. In orderto prevent a short-circuit phenomenon generated by a matter that the gapbetween the transparent resin substrates is narrow so that theincorporation of a contaminant and others are generated, it is allowableto use transparent electroconductive resin substrates in each of which atransparent insulating layer having a thickness in the range of severalnanometers to about 1 μm is formed on a transparent electroconductivefilm. When the light control film of the present invention is used in areflective-type light control window (in, for example, a rear viewingmirror for cars), a thin film of a electroconductive metal, such asaluminum, gold or silver, which is a reflecting body, may be useddirectly as an electrode.

<Light Control Film>

The light control film in the present invention can be formed, using alight control material, and the light control material includes a resinmatrix made of a polymeric medium, and a light control suspensiondispersed in the resin matrix to form a light control layer. The lightcontrol layer is sandwiched between two transparent electroconductiveresin substrates each having a primer layer for improving theadhesiveness of the substrate onto the light control layer, or issandwiched between two transparent electroconductive substrates one ofwhich has a primer layer and the other of which has not any primerlayer.

In order to obtain the light control film, a liquid light controlsuspension is first mixed with a polymeric medium into a homogeneousform to obtain a light control material made of a mixed liquid whereinthe light control suspension is dispersed, in the state of droplets, inthe polymeric medium.

Specifically, this process is as follows: A liquid wherein light controlparticles are dispersed in a solvent is mixed with a dispersing mediumfor light control suspension, and then the solvent is distilled off bymeans of a rotary evaporator or the like to prepare a light controlsuspension.

Next, the light control suspension and a polymeric medium are mixed witheach other to prepare a mixed liquid (light control material) whereinthe light control suspension is dispersed, in the state of droplets, inthe polymeric medium.

This light control material is applied into a constant thickness onto atransparent electroconductive resin substrate having a primer layer, andoptionally the solvent contained in the light control material is driedand removed. A high-pressure mercury lamp or the like is then used toradiate ultraviolet rays thereto, thereby curing the polymeric medium.As a result, a light control layer is formed wherein the light controlsuspension is dispersed, in the form of droplets, in a resin matrix madeof the cured polymeric medium. By changing the blend ratio between thepolymeric medium and the light control suspension variously, the lighttransmittance of the light control layer can be adjusted. Anothertransparent electroconductive resin substrate having a primer layer iscaused to adhere closely to the thus formed light control layer, therebyobtaining a light control film.

Alternatively, it is allowable to apply this light control material intoa constant thickness onto a transparent electroconductive resinsubstrate having a primer layer, optionally to dry and remove thesolvent contained in the light control material, to laminate anothertransparent electroconductive resin substrate having a primer layerthereon, and then to irradiate the lamination with ultraviolet rays tocure the polymer medium. Only one of the transparent electroconductiveresin substrates may be a transparent electroconductive resin substratehaving a primer layer. It is also allowable to form light control layersonto two transparent electroconductive resin substrates, respectively,and then to laminate the substrates onto each other to cause the lightcontrol layers to adhere closely to each other. The thickness of thelight control layer(s) is preferably in the range of 5 to 1,000 μm, morepreferably in the range of 20 to 100 μm.

The size (average droplet diameter) of the droplets of the light controlsuspension dispersed in the resin matrix is usually in the range of 0.5to 100 μm, preferably in the range of 0.5 to 20 μm, more preferably inthe range of 1 to 5 μm. The size of the droplets is decided inaccordance with the concentrations of the individual components thatconstitute the light control suspension, the viscosities of the lightcontrol suspension and the polymeric medium, the compatibility of thedispersing medium in the light control suspension with the polymericmedium, and others. The average droplet diameter can be calculated, forexample, by using an SEM to take a photograph or some other image of thelight control film along the direction toward one of its surfaces,measuring the diameters of arbitrarily-selected ones out of dropletstherein, and then getting the average value thereof. The diameter canalso be calculated by taking a viewing field image of the light controlfilm through an optical microscope, as digital data, into a computer,and then applying an image processing integration software thereto.

The primer treatment (the formation of the primer layer) onto one oreach of the transparent electroconductive resin substrates in thepresent invention can be conducted, for example, by applying thematerial for forming the primer layer onto the substrate, using a barcoater method, a Mayer bar coater method, an applicator method, a doctorblade method, a roll coater method, a die coater method, a comma coatermethod, a gravure coater method, a micro-gravure coater method, a rollbrush method, a spray coating method, an air knife coating method, animpregnation method, a curtain coating method, and others alone or incombination. At the time of the applying, it is allowable to dilute thematerial for forming the primer layer optionally with an appropriatesolvent, and then use the solution of the material for forming theprimer layer. When the solvent is used, it is necessary to apply thesolution onto the transparent electroconductive resin substrate and thento dry the resultant. The applied film, which is to be the primer layer,may be formed onto only a single surface of the transparentelectroconductive resin substrate, or onto each of the substrate as theneed arises.

The solvent used to form the primer layer may be any solvent as long asa solvent can dissolve the material for forming the primer layer, andcan be removed by drying or the like after the formation of the primerlayer. Examples thereof include isopropyl alcohol, ethanol, methanol,1-methoxy-2-propanol, 2-methoxyethanol, cyclohexanone, methyl isobutylketone, anisole, methyl ethyl ketone, acetone, tetrahydrofuran, toluene,heptane, cyclohexane, ethyl acetate, propylene glycol monomethyl etheracetate, diethyl diglycol, dimethyl diglycol, isoamyl acetate, and hexylacetate. A mixed solvent of two or more thereof may be used.

For the applying of the light control material, which is to be the lightcontrol layer, use is made of a known applying means, such as a barcoater, an applicator, a doctor blade, a roll coater, a die coater, or acomma coater. The light control material is applied onto the primerlayer laid on each of the transparent electroconductive resinsubstrates. Alternatively, in the case of using transparentelectroconductive resin substrates one of which has no primer layer, thelight control material may be applied directly onto the transparentelectroconductive resin substrate. At the time of the applying, thelight control material may be diluted with an appropriate solvent as theneed arises. When the solvent is used, it is necessary that after thediluted light control material is applied onto (each of) the transparentelectroconductive resin substrate(s), the substrate is dried.

The solvent used for applying the light control material may betetrahydrofuran, toluene, heptane, cyclohexane, ethyl acetate, ethanol,methanol, isoamyl acetate, hexyl acetate, or the like. In order to forma light control layer wherein the liquid light control suspension isdispersed, in the form of fine droplets, in the solid resin matrix, usemay be made of a method of using a homogenizer, an ultrasonichomogenizer, or the like to mix components of the light control materialwith each other to disperse the light control suspension into thepolymeric medium, a phase separation method based on the polymerizationof the resin component(s) in the polymeric medium, a phase separationmethod based on the volatilization of the solvent contained in the lightcontrol material, or a phase separation method depending on temperature,or some other method.

According to the above-mentioned process, a light control film can beprovided wherein the light transmittance can be adjusted arbitrarily bythe formation of an electric field. Also when no electric field isformed, this light control film is kept in a vividly colored state,wherein no light is scattered. When an electric field is formed, thefilm is converted into a transparent state. This capability exhibits aproperty that 200000 or more reversible repetitions can be attained. Inorder to promote the light transmittance in the transparent state, andto promote the vividness in the colored state, it is preferred to makethe refractive index of the liquid light control suspension equal tothat of the resin matrix.

About the power source used to operate the light control film, analternating current may be used, and the voltage thereof may be in therange of 10 to 100 volts (effective value), and the frequency thereofmay be in the range of 30 Hz to 500 kHz.

About the light control film of the present invention, the response timeto the electric field may be set into the range of 1 to 50 seconds whenthe film is discolored, and that may be set into the range of 1 to 100seconds when the film is colored.

About the endurance against ultraviolet rays, results of an ultravioletradiating test using ultraviolet rays of 750 W power and others,demonstrate that a stable variability is exhibited even after the lapseof 250 hours. Even when the film is allowed to stand still at −50 to 90°C. over a long period, the initial variability can be maintained.

When use is made of a method based on a water-used emulsion in theproduction of a light control film wherein a liquid crystal is used inthe prior art, the liquid crystal reacts with water so that the lightcontrol property is lost in many cases. Thus, there is caused a problemthat films having the same properties are not easily produced. In thepresent invention, use is made of not any liquid crystal but a liquidlight control suspension wherein light control particles are dispersed;thus, when no electric field is applied, the light control film lightdoes not cause light to be scattered and the film is in such a coloredstate that the vividness is excellent and no limitation is imposed ontothe viewing angle, which is different from situations according to theliquid-crystal-used light control films. By adjusting the content bypercentage of the light control particles, adjusting the droplet form orthe film thickness, or adjusting the electric field intensity, the lightvariation degree can be adjusted arbitrarily. In the light control filmof the present invention, no liquid crystal is used; therefore, thefollowing are also overcome: a change in the color tone and a fall inthe variability power that are based on the irradiation with ultravioletrays; and a response time lag following a voltage drop generated betweenthe periphery of the transparent electroconductive resin substrates andthe center thereof, the lag being peculiar to large-sized products.

When no electric field is applied to the light control film according tothe present invention, the film turns in a vividly colored state becauseof light absorption of the light control particles and dichroic effecton the basis of the Brownian movement of the light control particles inthe light control suspension. However, when an electric field is appliedthereto, the light control particles in the droplets or associateddroplets are arranged in parallel to the electric field, so that thefilm is converted into a transparent state. Since the film of thepresent invention is in a film state, the film solves the problems oflight control glass in the prior art, wherein a liquid light controlsuspension is used as it is, the problem being the following problems:the liquid suspension is not easily injected between two transparentelectroconductive resin substrates; a difference in hydraulic pressurebetween the upper and lower regions of the product easily causes anexpansion phenomenon of the lower region; and in accordance with theexternal environment, for example, the pressure of wind, the intervalbetween the substrates is changed so that the color phase is locallychanged; or a sealing member between the transparent electroconductivesubstrates is broken so that the light control material leaks.

In a case of a light control window according to the prior art wherein aliquid crystal is used, the liquid crystal is easily deteriorated byultraviolet rays and further the range of the use temperature thereof isalso narrow by thermal properties of a nematic liquid crystal.Furthermore, about optical properties thereof also, the followingproblems are caused: when no electric field is applied thereto, thewindow is turned in a milk-white semi-transparent state by lightscattering; and when an electric field is applied thereto, the window isnot completely turned vivid so that the opacified state remains.Accordingly, such a light control window cannot attain a displayfunction based on the blocking and transmission of light, which are usedas an action principle in existing liquid crystal display elements.However, the use of the light control film of the present inventionmakes it possible to solve such problems.

In the light control film of the present invention, the adhesivenessbetween the light control layer and the transparent electroconductiveresin substrates is strong. Thus, the film is an excellent light controlfilm which does not cause a problem that the light control layer ispeeled from the transparent electroconductive resin substrates in theproduction steps, a working step after the production of the film, orsome other step.

The light control film of the present invention can be preferably usedfor, e.g., an indoor or outdoor partition; a window glass plate or askylight window for building; various flat display elements used in theelectronic industry and for imaging instruments; alternate products forvarious gauge boards and existing liquid crystal display elements; alight shutter; various indoor and outdoor advertisement and guideindicating boards; window glass plates for an aircraft, a railwayvehicles and a ship; window glass plates, a back mirror and a sun rooffor a car; glasses; sunglasses; a sun visor; and other articles. Theusing manner of the light control film of the present invention may be adirect use of the film. In accordance with an article to which thepresent invention is applied, the light control film may be used in thestate that the film is sandwiched between two substrates, or in thestate that the film is adhered onto a single surface of a substrate. Thesubstrate may be, for example, a glass plate, or a polymeric filmequivalent to the above-mentioned transparent resin substrate.

The structure and the operation of the light control film according tothe present invention will be described in more detail with reference tothe drawings.

FIG. 1 is a schematic view of the structure of a light control film ofan aspect of the present invention. A light control layer 1 issandwiched between two transparent electroconductive resin substrates 4,which comprise two transparent resin substrates 5 a and a transparentelectroconductive film 5 a, each of transparent resin substrate 5 abeing coated with a transparent electroconductive film 5 a. A primerlayer 6 is arranged between the light control layer 1 and each of thetransparent electroconductive resin substrates 4. By switching a switch8, a power source 7 is connected or disconnected to the two transparentelectroconductive films 5 a. The light control layer 1 is composed of afilm-form resin matrix 2 obtained by curing (A) the resin with thesubstituent having the ethylenically unsaturated bond, with ultravioletrays, and a liquid-form light control suspension dispersed, in the formof droplets 3, in the resin matrix 2.

FIG. 2 are each a schematic view for describing the operation of thelight control film illustrated in FIG. 1, and each illustrate a casewhere the switch 8 is turned off to apply no electric field. In thiscase, incident rays 11 are absorbed, scattered or reflected in or onlight control particles 10, which are dispersed in a dispersing medium 9constituting the droplets 3 of the liquid-form light control suspension,by the Brownian movement of the light control particles 10. Thus, therays 11 cannot be transmitted. As illustrated in FIG. 3, however, whenthe switch 8 is connected, so as to apply an electric field, the lightcontrol particles 10 are arranged in parallel to an electric fieldformed by the applied electric field so that the incident rays 11 cometo pass between the arranged light control particles 10. In this way, alight transmitting function which causes neither scattering nor a fallin the transparency is produced.

EXAMPLES

The present invention will be more specifically described by way ofexamples and comparative examples of the present invention hereinafter.However, the present invention is not limited by these examples.

Production Example of Light Control Particles

In order to produce light control particles, in a 500 mL four-neckedflask equipped with a stirrer and a condenser tube, 4.5 g of iodide (JISextra pure reagent, manufactured by Wako Pure Chemical Industries, Ltd.)was dissolved in a solution composed of 87.54 g of a 15% by masssolution of nitrocellulose (trade name: 1/4 LIG, manufactured byBergerac NC Co.), diluted with isoamyl acetate (extra pure reagent,manufactured by Wako Pure Chemical Industries, Ltd.), 44.96 g of isoamylacetate, 4.5 g of dehydrated CaI₂ (for chemistry, manufactured by WakoPure Chemical Industries, Ltd.), 2.0 g of anhydrous ethanol (for organicsynthesis, manufactured by Wako Pure Chemical Industries, Ltd.), andpurified water (purified water, manufactured by Wako Pure ChemicalIndustries, Ltd.). Thereto was then added 3 g ofpyrazine-2,5-dicarboxylic acid dihydrate (manufactured by PolyCarbonIndustries), which was a base-forming material of the light controlparticles. The resultant was stirred at 45° C. for 3 hours to terminatethe reaction. Thereafter, the solid component was dispersed for 2 hoursby means of an ultrasonic disperser. At this time, the color tone of themixed liquid changed from brown to navy blue.

Next, in order to take out light control particles having specifiedsizes from the reaction solution, a centrifugal separator was used toseparate the light control particles. The reaction solution wascentrifuged at a rate of 750G for 10 minutes to remove theprecipitation. Furthermore, the solution was centrifuged at a rate of7390 G for 2 hours to remove the floated materials, and theprecipitation particles were collected. The precipitation particles weremade of a needle crystal having an average particle diameter of 0.36 μm,the diameter being measured by means of a submicron particle analyzer(N4MD, manufactured by Beckman Coulter, Inc.). The precipitationparticles were called the light control particles.

Production Example of a Light Control Suspension

The light control particles obtained in the item (Production example oflight control particles), the amount of which was 45.5 g, was added to50 g of a copolymer of butyl acrylate (Wako extra pure reagent,manufactured by Wako Pure Chemical Industries,Ltd.)/2,2,2-trifluoroethyl methacrylate (for industry, manufactured byKyoeisha Chemical Co., Ltd.)/2-hydroxyethyl acrylate (Wako first classreagent, manufactured by Wako Pure Chemical Industries, Ltd.) (ratio bymole between the monomers: 18/1.5/0.5, weight-average molecular weight:2,000, refractive index: 1.4719), and then a stirrer was used to mix thecomponents with each other for 30 minutes. Next, a rotary evaporator wasused to remove isoamyl acetate at 80° C. in a vacuum having a reducedpressure of 133 Pa for 3 hours to produce a stable liquid-form lightcontrol suspension wherein the light control particles neitherprecipitated nor aggregated.

Production Example of an Energy Beam Curable Silicone Resin

Into a four-necked flask equipped with a Dean-Stark trap, a condensertube, a stirrer and a heating device were charged 17.8 g ofsilanol-both-terminated polydimethylsiloxane (reagent, manufactured byChisso Corp.), 62.2 g of silanol-both-terminatedpolydimethyldiphenylsiloxane (reagent, manufactured by Chisso Corp.), 20g of (3-acryloxypropyl)methyldimethoxysilane (reagent, manufactured byChisso Corp.), and 0.1 g of 2-ethylhexanetin (manufactured by Wako PureChemical Industries, Ltd.). In heptane, the solution was refluxed at100° C. for 3 hours to conduct a reaction. Next, thereto was added 25 gof trimethylethoxysilane (reagent, manufactured by Chisso Corp.), andthe resultant was refluxed for 2 hours to cause a dealcoholizationreaction, and then a rotary evaporator was used to remove heptane in avacuum having a reduced pressure of 100 Pa at 80° C. for 4 hours toobtain an energy beam curable silicone resin having a weight-averagemolecular weight of 35000, and a refractive index of 1.4745. From thehydrogen integrated-intensity ratio according to NMR, the concentrationof ethylenically unsaturated bonds in this resin was 0.31 mol/kg. Theethylenically unsaturated bond concentration was measured by a methoddescribed below.

[Method for Measuring the Ethylenically Unsaturated Bond Concentration]

The ethylenically unsaturated bond concentration (mol/kg) was measuredfrom the hydrogen integrated-intensity ratio according to NMR (using anintegrated value of hydrogen in the ethylenically unsaturated bond near6 ppm, an integrated value of hydrogen in phenyl groups near 7.5 ppm,and an integrated value of hydrogen in methyl groups near 0.1 ppm). Thesolvent for the measurement was rendered CDCl₃. In the resin produced asdescribed above, the ratio by mass calculated out from the hydrogenintegrated-intensity ratio according to NMR was as follows: the methylgroups/the phenyl groups/the ethylenically unsaturated groups was11/6.4/1. The proportion of the ethylenically unsaturated groups in thewhole was 5.4%, and the number of the ethylenically unsaturated groupsper molecule was 9.35 from the individual molecular weights. Thus, themole number per kilogram was calculated into 0.31 mol/kg.

Example 1

The light control suspension obtained in the item (Production example ofa light control suspension), the amount of which was 2.5 g, was added to10 g of the energy beam curable silicone resin obtained in the item(Production example of an energy beam curable silicone resin), 0.2 g ofbis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Ciba SpecialtyChemicals Inc.) as a photopolymerization initiator, and 0.3 g ofdibutyltin dilaurate as a coloration inhibitor, and then the componentswere mechanically mixed with each other for 1 minute to produce a lightcontrol material.

Separately, an applicator method was used under a condition that the gaptherein was set to 10 μm to apply a solution wherein a mixture ofpentaerythritol triacrylate and pentaerythritol tetraacrylate (tradename: ARONIX M-305, manufactured by Toagosei Co., Ltd.) was dissolved ina mixed solvent of methyl ethyl ketone and cyclohexanone (the ratiotherebetween=1:1) to give a concentration of 5.0% by mass, as a solutionat the time of primer-layer-formation, onto a transparentelectroconductive resin substrate made of a PET film (300R, manufacturedby Toyobo Co., Ltd., thickness: 125 μm) which was coated with atransparent electroconductive film (thickness: 300 Å) made of ITO(indium tin oxide) and which had a surface electric resistance value of200 to 700Ω in such a manner that the solution was applied onto thewhole of the surface of the transparent electroconductive film. Theworkpiece was dried at 50° C. for 30 seconds, at 60° C. for 30 seconds,and 70° C. for 1 minute, and then irradiated with UV at 1000 mJ/cm²(from a metal halide lamp) to photocure the applied solution, therebyforming a primer layer. At this time, a photopolymerization initiator(1-hydroxy-cyclohexyl phenyl ketone) was added thereto in an amount of3% by mass of the ARONIX M-305.

The thickness of the primer layer was 68 nm.

The light control material obtained as above was applied onto the wholeof the surface of the transparent electroconductive resin substrate onwhich the primer layer was formed. Next, thereon was laminated the sametransparent electroconductive resin substrate, on which a primer layerwas formed in the same way, so as to face the primer layer onto theapplied layer of the light control material. In this way, they werecaused to adhere closely to each other. A metal halide lamp was used toradiate ultraviolet rays of 3000 mJ/cm² power onto the laminatedtransparent electroconductive resin substrates from the polyester filmside thereof, so as to produce a light control film of 340 μm thicknesswherein a film-form light control layer of 90 μm thickness, in which thelight control suspension was dispersed and formed in a resin matrixcured with the ultraviolet rays so as to be in the form of sphericaldroplets, was sandwiched between the transparent electroconductive resinsubstrates.

Next, from an end region of this light control film, the light controllayer was removed to make the transparent electroconductive film in theend region naked in order to attain electroconduction forvoltage-application (see FIG. 4). The size (average droplet diameter) ofthe droplets of the light control suspension in the light control filmwas 3 μm on average. The light transmittance of the light control filmwas 1.1% when no alternating voltage was applied thereto (theelectric-field-unapplied time). When an alternating voltage of 100 V(effective value) having a frequency of 50 Hz was applied thereto, thelight transmittance of the light control film was 47%. The ratio betweenthe light transmittance at the electric-field-applied time and that atthe electric-field-unapplied time was as large as 47, and was good.

The end region of the light control film (the region where the lightcontrol layer was removed so that the transparent electroconductive filmwas made naked) was observed with the naked eye. As a result, curves ofthe transparent electroconductive resin substrates toward the center ofthe light control film in the thickness direction were very small (seeFIG. 4). Measurements as described below were made for evaluations ofthe size of the droplets of the light control suspension in the lightcontrol film, the light transmittance of the light control film, thebonding strength between the light control layer and the transparentelectroconductive resin substrates, the primer layer film thickness, thetransferability of the primer layers, the tackiness, and the peelingmode.

The results are shown in Table 1.

[Method for Measuring the Size of the Droplets of the Light ControlSuspension]

An SEM photograph of the light control film was taken along thedirection toward one of the surfaces of the light control film. Thediameters of arbitrarily-selected ones out of the droplets therein weremeasured, and the average value thereof was calculated.

[Method for Measuring the Light Transmittance of the Light Control Film]

A spectroscopic color-difference meter SZ-Σ90 (manufactured by NipponDenshoku Industries Co., Ltd.) was used to measure the Y value (%) inthe state that the used light source was an A light source and theviewing angle was set to 2 degrees. The Y value was defined as the lighttransmittance. The light transmittance was measured at theelectric-field-applied time and at the electric-field-unapplied time.

[Method for Measuring the Bonding Strength of the Light Control Layer]

The bonding strength was measured, using a rheometer, STROGRAPH E-S(manufactured by Toyo Seiki Seisaku-sho Ltd.) to peel one of thetransparent electroconductive resin substrates from the light controllayer of the light control film under the following conditions: thepeeling angle was 90°, the loading weight was 50 N, and the pulling-upspeed was 50 mm/min

[Method for Measuring the Film Thickness of the Primer Layers]

The film thickness of the primer layers was measured by use of aninstantaneous spectrophotometer F-20 (manufactured by Filmetrics Japan,Inc.).

[Method for Evaluating the Transferability]

Any one of the primer layers was put onto a PET surface of an ITO/PETproduct, and then a weight of about 1 kg was put on the resultantmatter. In this state, the matter was stored for one week, and it waschecked with the naked eye whether or not the primer layer wastransferred on the PET surface of the ITO/PET product. A case where theproportion of the transferred area was 5% or less of the whole of theprimer-applied area was evaluated as ◯; a case where the proportion ofthe transferred area was from 5 to 30% of the whole of theprimer-applied area, Δ; and a case where the proportion was 30% or more,x.

[Method for Evaluating the Tackiness]

The tackiness of the primer-layer-formed ITO/PET (any one of theprimer-layer-formed transparent electroconductive resin substratesproduced in Example 1 before the light control layer was formed) wasevaluated as follows:

First, a light control material was applied onto the primer-layer-formedITO/PET (any one of the primer-layer-formed transparentelectroconductive resin substrates produced in Example 1 before thelight control layer was formed).

When the light control film was produced in a roll-to-roll manner, theother primer-layer-formed ITO/PET (the other primer-layer-formedtransparent electroconductive resin substrate produced in Example 1before the light control layer was formed) was laminated onto theabove-mentioned substrate, on which the light control material hadalready been formed. At this time, it was necessary to adjust theposition of the other primer-layer-formed ITO/PET delicately into adirection perpendicular to the applying direction, so as to put the twoonto each other precisely. A case where the position adjustment was ableto be easily attained in the state that the primer layer of the otherprimer-layer-formed ITO/PET contacted a tension-applying metallic rollwas evaluated as ◯; a case where the adjustment was not easily attainedbut was allowable, Δ; and a case where the position adjustment wasdifficult, x.

[Method for Evaluating the Peeling Mode]

About the light control film from which the transparentelectroconductive resin substrates were peeled, the film being obtainedafter the measurement of the bonding strength, the manner that thetransparent electroconductive resin substrates were peeled from thelight control film, was evaluated in accordance with an evaluationcriterion decided as described below. A case where the light controllayer remained on each of the two transparent electroconductive resinsubstrates, and at the time of the peeling, the inside of the lightcontrol layer was broken was defined as cohesive failure. A case wherethe light control layer remained on only one of the transparentelectroconductive resin substrates, and at the time of the peeling, thelight control layer itself was not broken (only the substrates werepeeled) was defined as interfacial peeling.

Example 2

A light control film was produced and then the various measurements weremeasured thereabout in the same way as in Example 1 except that: amicro-gravure method (mesh #: 150) was used to apply, as the solution atthe time of the primer-layer-formation, a solution wherein a productAY42-150 (trade name) manufactured by Dow Corning Toray Co., Ltd. wasdissolved in a mixed solvent of isopropyl alcohol and1-methoxy-2-propanol (ratio therebetween=1:1) to give a concentration of1.0% by mass onto the whole of the surface of the transparentelectroconductive film of each of the transparent electroconductiveresin substrates; and the workpiece was dried at 50° C. for 30 seconds,at 60° C. for 30 seconds, and 70° C. for 1 minute, and then irradiatedwith UV at 1000 mJ/cm² (a metal halide lamp), so as to photocure theapplied solution, thereby forming each primer layer. The results areshown in Table 1. The product AY42-150 contains a photopolymerization(1-hydroxy-cyclohexyl phenyl ketone). The thickness of the primer was 68nm.

The product AY42-150, which was used to form the primer layer, is amixture that contains SiO₂ fine particles and is composed of adipentaerythritol acrylate, a methacrylic acid monomer, and a siloxanecompound.

Example 3

A light control film was produced and then the various measurements weremeasured thereabout in the same way as in Example 1 except that: anapplicator method was used under a condition that the gap therein wasset to 10 vim to apply, as the solution at the time of theprimer-layer-formation, a solution wherein an acrylic acid adduct ofglycerin diglycidyl ether (trade name: EPOXY ESTER 80MFA, manufacturedby Kyoeisha Chemical Co., Ltd.) was dissolved in a mixed solvent ofmethyl ethyl ketone and cyclohexanone (ratio therebetween=1:1) to give aconcentration of 5.0% by mass onto the whole of the surface of thetransparent electroconductive film of each of the transparentelectroconductive resin substrates; and the workpiece was dried at 50°C. for 30 seconds, at 60° C. for 30 seconds, and 70° C. for 1 minute,and then irradiated with UV at 1000 mJ/cm² (a metal halide lamp), so asto photocure the applied solution, thereby forming each primer layer.The results are shown in Table 1. At this time, a photopolymerizationinitiator (1-hydroxy-cyclohexyl phenyl ketone) was added thereto in anamount of 3% by mass of the product EPOXY ESTER 80MFA.

The thickness of the primer layer was 95 nm.

Example 4

A light control film was produced and then the various measurements weremeasured thereabout in the same way as in Example 1 except that: amicro-gravure method (mesh #: 150) was used to apply, as the solution atthe time of the primer-layer-formation, a solution wherein a productUVHC 7000 (trade name) manufactured by Momentive Performance MaterialsJapan LLC was dissolved in isopropyl alcohol to give a concentration of1.0% by mass onto the whole of the surface of the transparentelectroconductive film of each of the transparent electroconductiveresin substrates; and the workpiece was dried at 50° C. for 30 seconds,at 60° C. for 30 seconds, and 70° C. for 1 minute, and then irradiatedwith UV at 500 mJ/cm² (a mercury lamp), so as to photocure the appliedsolution, thereby forming each primer layer. The results are shown inTable 1. The product UVHC 7000 contains a photopolymerization(1-hydroxy-cyclohexyl phenyl ketone) in an amount of 3.5% by mass of theproduct UVHC 7000.

The thickness of the primer was 35 nm.

The product UVHC 7000, which was used to form the primer layer, containsno filler but contains an IPDI-skeleton-containing pentaerythritolurethane acrylate, tripropylene glycol diacrylate, and 1,6-hexanedioldiacrylate.

TABLE 1 Light Light transmittance transmittance Material of Film whenelectric when electric Bonding primer layer thickness field appliedfield unapplied strength Peeling Items (% by mass) (nm) (%) (%) (N/m)Tackiness Ttansferability mode Example 1 M-305 68 47 1.1 14.3 ◯ ◯Cohesive (5.0) failure Example 2 AY42-150 68 48 0.8 12.2 ◯ ◯ Cohesive(1.0) failure Example 3 Epoxy ester 95 46 1.1 14.8 ◯ ◯ Cohesive 80MFAfailure (5.0) Example 4 UVHC7000 35 46 1.0 13.2 ◯ ◯ Cohesive (1.0)failure

Comparative Example 1

A light control film was produced and then the various measurements weremeasured thereabout in the same way as in Example 1 except that PETfilms (300R, manufactured by Toyobo Co., Ltd., thickness: 125 μm) whichwere each coated with a transparent electroconductive film made of ITOwere used, as they were, without forming any primer layer onto each ofthe films. The results are shown in Table 2.

Comparative Example 2

A light control film was produced and then the various measurements weremeasured thereabout in the same way as in Example 1 except that: anapplicator method was used under a condition that the gap was set to 10μm to apply, as the solution at the time of the primer-layer-formation,a solution wherein dipentaerythritol hexaacrylate (trade name: ARONIXM-405, manufactured by Toagosei Co., Ltd.) was dissolved in a mixedsolvent of methyl ethyl ketone and cyclohexanone (ratiotherebetween=1:1) to give a concentration of 5.0% by mass onto the wholeof the surface of the transparent electroconductive film of each of thetransparent electroconductive resin substrates; and the workpiece wasdried at 50° C. for 30 seconds, at 60° C. for 30 seconds, and 70° C. for1 minute, and then irradiated with UV at 1000 mJ/cm² (a metal halidelamp), so as to photocure the applied solution, thereby forming eachprimer layer. The results are shown in Table 2. At this time, aphotopolymerization initiator (1-hydroxy-cyclohexyl phenyl ketone) wasadded thereto in an amount of 3% by mass of the product ARONIX M-405.

The thickness of the primer layer was 77 nm.

Comparative Example 3

A light control film was produced and then the various measurements weremeasured thereabout in the same way as in Example 1 except that: anapplicator method was used under a condition that the gap was set to 10μm to apply, as the solution at the time of the primer-layer-formation,a solution wherein isocyanuric-acid-EO modified triacrylate (trade name:ARONIX M-315, manufactured by Toagosei Co., Ltd.) was dissolved in amixed solvent of methyl ethyl ketone and cyclohexanone (ratiotherebetween=1:1) to give a concentration of 5.0% by mass onto the wholeof the surface of the transparent electroconductive film of each of thetransparent electroconductive resin substrates; and the workpiece wasdried at 50° C. for 30 seconds, at 60° C. for 30 seconds, and 70° C. for1 minute, and then irradiated with UV at 1000 mJ/cm² (a metal halidelamp), so as to photocure the applied solution, thereby forming eachprimer layer. The results are shown in Table 2. At this time, aphotopolymerization initiator (1-hydroxy-cyclohexyl phenyl ketone) wasadded thereto in an amount of 3% by mass of the product ARONIX M-315.

The thickness of the primer layer was 82 nm.

Comparative Example 4

A light control film was produced and then the various measurements weremeasured thereabout in the same way as in Example 1 except that: anapplicator method was used under a condition that the gap was set to 10μm to apply, as the solution at the time of the primer-layer-formation,a solution wherein acrylic acid dimer (trade name: ARONIX M-5600,manufactured by Toagosei Co., Ltd.) was dissolved in a mixed solvent ofmethyl ethyl ketone and cyclohexanone (ratio therebetween=1:1) to give aconcentration of 5.0% by mass onto the whole of the surface of thetransparent electroconductive film of each of the transparentelectroconductive resin substrates; and the workpiece was dried at 50°C. for 30 seconds, at 60° C. for 30 seconds, and 70° C. for 1 minute,and then irradiated with UV at 1000 mJ/cm² (a metal halide lamp), so asto photocure the applied solution, thereby forming each primer layer.The results are shown in Table 2. At this time, a photopolymerizationinitiator (1-hydroxy-cyclohexyl phenyl ketone) was added thereto in anamount of 3% by mass of the product ARONIX M-5600.

The thickness of the primer layer was 48 nm.

Comparative Example 5

A light control film was produced and then the various measurements weremeasured thereabout in the same way as in Example 1 except that: anapplicator method was used under a condition that the gap was set to 10μm to apply, as the solution at the time of the primer-layer-formation,a solution wherein monohydroxyethyl phthalate acrylate (trade name:ARONIX M-5400, manufactured by Toagosei Co., Ltd.) was dissolved in amixed solvent of methyl ethyl ketone and cyclohexanone (ratiotherebetween=1:1) to give a concentration of 5.0% by mass onto the wholeof the surface of the transparent electroconductive film of each of thetransparent electroconductive resin substrates; and the workpiece wasdried at 50° C. for 30 seconds, at 60° C. for 30 seconds, and 70° C. for1 minute, and then irradiated with UV at 1000 mJ/cm² (a metal halidelamp), so as to photocure the applied solution, thereby forming eachprimer layer. The results are shown in Table 2. At this time, aphotopolymerization initiator (1-hydroxy-cyclohexyl phenyl ketone) wasadded thereto in an amount of 3% by mass of the product ARONIX M-5400.

The thickness of the primer layer was 56 nm

Comparative Example 6

A light control film was produced and then the various measurements weremeasured thereabout in the same way as in Example 1 except that: anapplicator method was used under a condition that the gap was set to 10μm to apply, as the solution at the time of the primer-layer-formation,a solution wherein ω-carboxy-polycaprolactone monoacrylate (trade name:ARONIX M-5300, manufactured by Toagosei Co., Ltd.) was dissolved in amixed solvent of methyl ethyl ketone and cyclohexanone (ratiotherebetween=1:1) to give a concentration of 5.0% by mass onto the wholeof the surface of the transparent electroconductive film of each of thetransparent electroconductive resin substrates; and the workpiece wasdried at 50° C. for 30 seconds, at 60° C. for 30 seconds, and 70° C. for1 minute, and then irradiated with UV at 1000 mJ/cm² (a metal halidelamp), so as to photocure the applied solution, thereby forming eachprimer layer. The results are shown in Table 2. At this time, aphotopolymerization initiator (1-hydroxy-cyclohexyl phenyl ketone) wasadded thereto in an amount of 3% by mass of the product ARONIX M-5300.

The thickness of the primer layer was 72 nm

Comparative Example 7

A light control film was produced and then the various measurements weremeasured thereabout in the same way as in Example 1 except that: anapplicator method was used under a condition that the gap was set to 10μm to apply, as the solution at the time of the primer-layer-formation,a solution wherein 1,6-hexanediol diacrylate (trade name: LIGHT ACRYLATE1,6HX-A, manufactured by Kyoeisha Chemical Co., Ltd.) was dissolved in amixed solvent of methyl ethyl ketone and cyclohexanone (ratiotherebetween=1:1) to give a concentration of 5.0% by mass onto the wholeof the surface of the transparent electroconductive film of each of thetransparent electroconductive resin substrates; and the workpiece wasdried at 50° C. for 30 seconds, at 60° C. for 30 seconds, and 70° C. for1 minute, and then irradiated with UV at 1000 mJ/cm² (a metal halidelamp), so as to photocure the applied solution, thereby forming eachprimer layer. The results are shown in Table 2. At this time, aphotopolymerization initiator (1-hydroxy-cyclohexyl phenyl ketone) wasadded thereto in an amount of 3% by mass of the product LIGHT ACRYLATE1,6HX-A.

The thickness of the primer layer was 55 nm

Comparative Example 8

A light control film was produced and then the various measurements weremeasured thereabout in the same way as in Example 1 except that: anapplicator method was used under a condition that the gap was set to 10μm to apply, as the solution at the time of the primer-layer-formation,a solution wherein dimethylol-tricyclodecane diacrylate (trade name:LIGHT ACRYLATE DCP-A, manufactured by Kyoeisha Chemical Co., Ltd.) wasdissolved in a mixed solvent of methyl ethyl ketone and cyclohexanone(ratio therebetween=1:1) to give a concentration of 5.0% by mass ontothe whole of the surface of the transparent electroconductive film ofeach of the transparent electroconductive resin substrates; and theworkpiece was dried at 50° C. for 30 seconds, at 60° C. for 30 seconds,and 70° C. for 1 minute, and then irradiated with UV at 1000 mJ/cm² (ametal halide lamp), so as to photocure the applied solution, therebyforming each primer layer. The results are shown in Table 2. At thistime, a photopolymerization initiator (1-hydroxy-cyclohexyl phenylketone) was added thereto in an amount of 3% by mass of the productLIGHT ACRYLATE DCP-A.

The thickness of the primer layer was 45 nm.

TABLE 2 Light Light transmittance transmittance Material of Film whenelectric when electric Bonding primer layer thickness field appliedfield unapplied strrength Peeling Items (% by mass) (nm) (%) (%) (N/m)Tackiness Ttansferability mode Comparative No primer — 46 1.1 0.5 ◯ ◯Interfacial Example 1 peeling Comparative M-405 77 47 0.9 4.9 ◯ ◯Interfacial Example 2 (5.0) peeling Comparative M-315 82 47 1.1 2.1 X XInterfacial Example 3 (5.0) peeling Comparative M-5600 48 45 0.9 3.1 Δ XInterfacial Example 4 (5.0) peeling Comparative M-5400 56 47 1.0 1.5 Δ ΔInterfacial Example 5 (5.0) peeling Comparative M-5300 72 48 1.1 5.1 Δ XInterfacial Example 6 (5.0) peeling Comparative 1,6HX-A 55 47 0.9 2.2 XΔ Interfacial Example 7 (5.0) peeling Comparative DCP-A 45 46 1.0 1.6 XX Interfacial Example 8 (5.0) peeling

As shown in Tables 1 and 2, about the light transmittances at theelectric-field-applied time and at the electric-field-unapplied time, adifference was hardly generated between Comparative Example 1 and eachof the Examples. However, in Comparative Example 1, wherein no primerwas formed, and Comparative Examples 2 to 8, each of which primer layersother than the primer layers in the present invention were formed, thebonding strength was remarkably small, and further a peel of the lightcontrol layer from the transparent electroconductive resin substrates oreither one thereof was generated at the interface between the lightcontrol layer and the substrate(s).

By contrast, in each of the Examples, by the use of the primer layers,which were each made of a material containing a (meth)acrylate having inthe molecule thereof a hydroxyl group, the bonding strength was largelyimproved and a peel was generated in a cohesive failure mode. Thus, theadhesiveness was able to be largely improved while the light controlproperty was kept.

DESCRIPTION OF REFERENCE NUMERALS

-   1 Light control layer-   2 Resin matrix-   3 Droplet-   4 Transparent electroconductive resin substrate-   5 a Transparent electroconductive film-   5 b Transparent resin substrate-   6 Primer layer-   7 Power source-   8 Switch-   9 Dispersing medium-   10 Light control particle-   11 Incident light ray-   12 Transparent electroconductive film surface made naked by removing    a light control layer-   13 Lead through which a voltage is applied to transparent    electroconductive film

1. A light control film, comprising: two transparent electroconductiveresin substrates; and a light control layer sandwiched between the twotransparent electroconductive resin substrates, the light control layercomprising: a resin matrix; and a light control suspension dispersed inthe resin matrix, wherein at least one of the transparentelectroconductive resin substrates has, on the light control layer sidethereof, a primer layer, and the primer layer is made of a thin filmcomprising a material containing a (meth)acrylate having, in themolecule thereof, a hydroxyl group.
 2. The light control film accordingto claim 1, wherein the hydroxyl group is an alcoholic hydroxyl group.3. The light control film according to claim 1, wherein the(meth)acrylate having in the molecule thereof a hydroxyl group, is a(meth)acrylate having a pentaerythritol skeleton.
 4. The light controlfilm according to claim 1, wherein the primer layer contains oxide fineparticles.
 5. The light control film according to claim 4, wherein theoxide fine particles are any one of SiO₂, ITO and ZrO₂, or a mixturethereof.
 6. The light control film according to claim 5, wherein theprimer layer is made of a thin film wherein the (meth)acrylate isthermally cured or optically cured.
 7. The light control film accordingto claim 1, wherein the film thickness of the primer layer is 500 nm orless.
 8. The light control film according to claim 2, wherein the primerlayer contains oxide fine particles.
 9. The light control film accordingto claim 8, wherein the oxide fine particles are any one of SiO₂, ITOand ZrO₂, or a mixture thereof.
 10. The light control film according toclaim 9, wherein the primer layer is made of a thin film wherein the(meth)acrylate is thermally cured or optically cured.
 11. The lightcontrol film according to claim 8, wherein the primer layer is made of athin film wherein the (meth)acrylate is thermally cured or opticallycured.
 12. The light control film according to claim 3, wherein theprimer layer contains oxide fine particles.
 13. The light control filmaccording to claim 12, wherein the oxide fine particles are any one ofSiO₂, ITO and ZrO₂, or a mixture thereof.
 14. The light control filmaccording to claim 3, wherein the primer layer is made of a thin filmwherein the (meth)acrylate is thermally cured or optically cured. 15.The light control film according to claim 1, wherein the primer layer ismade of a thin film wherein the (meth)acrylate is thermally cured oroptically cured.
 16. The light control film according to claim 2,wherein the primer layer is made of a thin film wherein the(meth)acrylate is thermally cured or optically cured.
 17. The lightcontrol film according to claim 3, wherein the primer layer is made of athin film wherein the (meth)acrylate is thermally cured or opticallycured.
 18. The light control film according to claim 4, wherein theprimer layer is made of a thin film wherein the (meth)acrylate isthermally cured or optically cured.
 19. The light control film accordingto claim 6, wherein the film thickness of the primer layer is 500 nm orless.
 20. The light control film according to claim 5, wherein the filmthickness of the primer layer is 500 nm or less.